1. Field of the Invention
The present invention generally relates to the field of spinal surgery. In particular, the present invention relates to the field of surgical access to the spine.
2. Background
Spinal fusion is a procedure that promotes fusing or growing together of two or more vertebrae in the spine. Spinal fusion can be performed to:                straighten a spine deformed by scoliosis, neuromuscular disease, cerebral palsy, or other disorder;        prevent further deformation;        support a spine weakened by infection or tumor;        reduce or prevent pain from pinched or injured nerves;        compensate for injured vertebrae or disks.        
One of the goals of spinal fusion procedure is to unite two or more vertebrae to prevent them from moving independently of each other. This may be done to improve posture, increase ability to ventilate the lungs, prevent pain, or treat spinal instability and reduce the risk of nerve damage. According to the American Academy of Orthopedic Surgeons, approximately a quarter-million spinal fusions are performed each year, half on the upper and half on the lower spine.
The spine is a series of individual bones called vertebrae, separated by cartilaginous disks. The spine includes seven cervical (neck) vertebrae, 12 thoracic (chest) vertebrae, five lumbar (lower back) vertebrae, and the fused vertebrae in the sacrum and coccyx that help to form the hip region. While the shapes of individual vertebrae differ among these regions, each is essentially a short hollow tube containing the bundle of nerves known as the spinal cord. Individual nerves, such as those carrying messages to the arms or legs, enter and exit the spinal cord through gaps between vertebrae. The spinal disks act as shock absorbers, cushioning the spine, and preventing individual bones from contacting each other. Disks also help to hold the vertebrae together. The weight of the upper body is transferred through the spine to the hips and the legs. The spine is held upright through the work of the back muscles, which are attached to the vertebrae. While the normal spine has no side-to-side curve, it does have a series of front-to-back curves, giving it a gentle “S” shape. The spine curves in at the lumbar region, back out at the thoracic region, and back in at the cervical region.
One of the types of spinal fusion procedures is a posterior spinal fusion surgery. This procedure is performed posteriorly, or from the back of patient, as opposed to anteriorly, or through the abdomen. There are three know posterior fusion techniques (all three are typically performed with pedicle screw fixation). The first is a posterolateral gutter fusion surgery. This type of spinal fusion involves placing bone graft in the posterolateral portion of the spine (a region just outside the back of the spine). The second is a posterior lumbar interbody fusion (“PLIF”) surgery. A PLIF involves placing bone graft and/or spinal implant (e.g., cage) directly into the disc space in the front of the spine. The third is a transforaminal lumbar interbody fusion (“TLIF”) surgery. A TLIF is essentially like an extended PLIF, as it also involves expanding the disc space by removing one entire facet joint (whereas a PLIF usually involves gaining access to the disc space by removing a portion of the facet joints on each side of the spine).
There have been various approaches and systems for performing posterior spinal surgery. Some conventional systems further include titanium construction that is compatible with current CT and MRI scanning technology, low profile implant systems, top-loading and top-tightening systems, and other parameters. Some systems also include cross-connectors that allow one-piece implant to be applied to a dual-rod construct for a top-loading approach.
The conventional devices and systems have a number of disadvantages. These devices do not provide flexibility when adjusting the devices either prior to, during, or after their placement into the patient. Thus, these devices force a surgeon to utilize a specific configuration, leaving very little room for adjustment in accordance with patient's physiological characteristics and needs.
In some embodiments, the present invention relates to a minimally invasive bone screw placement system that allows a surgeon to implant one or more bone screws into the spine and connect he screws with a wire or any other device, wherein the system does not require any incisions in excess of the bone screw incisions.